What does charging an EV actually cost?
The formula behind EV charging cost: battery size × charge percentage × electricity price, plus the charging losses most estimates forget.
The basic math
Charging cost is energy times price: a 75 kWh battery charged from 20% to 80% takes in 45 kWh, and at 0.30 per kWh that is about 15 in whatever currency you pay. The same charge costs wildly different amounts depending on where you plug in — home night tariffs can be a quarter of the price of a DC fast charger.
One correction most quick estimates skip: charging is not lossless. On a home AC charger, 5–15% of the energy you pay for becomes heat in the onboard charger instead of range. Paying for 50 kWh to put 45 kWh in the battery is normal, which is why our calculator asks for an efficiency figure (90% is a sensible default).
Comparing to fuel
To compare with a petrol car, work out cost per distance. An EV using 18 kWh per 100 km at 0.30 per kWh costs 5.40 per 100 km at home. The same trip in a car burning 7 L per 100 km at 1.80 per liter costs 12.60 — but the comparison flips at expensive fast chargers, where per-kWh prices can approach petrol-equivalent costs.
Why the 20–80% window keeps appearing
Charging slows dramatically above roughly 80% — the battery management system tapers the current to protect the cells. For road trips, charging from 10% to 80% and driving on is usually faster than waiting for 100%. For daily use, staying in the middle of the range is also gentler on long-term battery health; save full charges for days you need the range.
Try related tools
- EV charging cost — What a charge costs from battery size, price per kWh, and losses.
- Percentage calculator — What is X% of Y, and X is what percent of Y.